CHICAGO (AFP) — US researchers said Monday they have conclusive proof to show that women who drink a lot of caffeine on a daily basis in the early months of pregnancy have an elevated risk of miscarriage, settling a longstanding debate over the issue.
To be absolutely safe, expectant mothers should avoid caffeinated beverages of any kind during the first five months of pregnancy, the researchers said in a paper published in the American Journal of Obstetrics and Gynecology.
The concept that pregnant women may be putting their babies in jeopardy by drinking large amounts of caffeine on a daily basis is not new.
Previous studies have suggested that consumption of three cups of coffee, or 300mg of caffeine a day, corresponds to an elevated risk of miscarriage compared to women who eschew the stimulant altogether.
However, critics argued that the results of those studies were skewed by the fact that women with healthy pregnancies tended to avoid coffee or caffeine because of morning sickness.
In order to get to the bottom of the issue, researchers with Kaiser Permanente monitored more than 1,000 women as they went through their pregnancies -- all of whom continued drinking coffee or caffeinated beverages in the same quantities as they did before conceiving.
The results were unequivocal.
The researchers found that a woman's risk of miscarriage increased in line with rising daily caffeine consumption, be it from coffee, tea, hot chocolate, caffeinated beverages, or a combination of all of these.
Women who consumed 200mg or more of caffeine a day had twice the risk of losing their baby as women who avoided the stimulant entirely.
For the purposes of this study, 200mg was said to be equivalent to two 7.5 oz cups of coffee or five 12-oz cans of a caffeinated soda drink a day.
"Women should consider giving up caffeine for the first three or four months of their pregnancy," said De-Kun Li, an epidemiologist with Kaiser Permanente's Division of Research in Oakland, California.
"If they have to have caffeine, they should limit it to one cup of coffee a day or switch to decaf."
Li noted that the study did not identify how much caffeine a mother-to-be could safely consume, and urged mothers to play it safe, noting that this is one of the few risk factors for miscarriage that they can control.
Scientists believe caffeine can be detrimental to the fetus because it readily crosses the placenta but cannot be easily metabolized by the fetus's under-developed metabolic system.
The stimulant can also cause blood vessels to constrict, leading to decreased blood flow to the placenta.
Researchers with Kaiser Permanente, a health care organization, studied 1,063 pregnant women between October 1996 and October 1998 for this study.
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